District plans should manage local scale effects of land transport noise and ensure long term, cumulative impacts of noise are prevented. The choice of land use planning options depends largely on the existing environment, planning provisions and available funding. For example, a busy central city area will require a different approach compared with areas subject to future residential subdivision and semi-rural living.

District plan responses can involve the following steps:

1) Setting acceptable noise levels

It is important to establish existing noise levels when developing objectives, policies and rules on land transport noise.

Noise can be modelled for transport corridors to estimate existing and future noise levels. Understanding the noise baseline assists with the implementation of appropriate policy measures such as objectives and rules. A number of tools are available to predict noise levels from transport corridors. The UK Calculation of Road Traffic Noise (CRTN) is the most widely recognised in New Zealand.

Most urban councils will have a good understanding of current noise prone areas. These tend to be along key transport routes where there is a high level of land use development, particularly residential. Monitoring of traffic related noise complaints can help identify problem areas but to date such monitoring has not been applied in any systematic manner.

identify suitable methods to manage the effects of land transport noise

work with NZTA, the regional council and other councils within their region to implement the regional land transport strategy, any existing corridor plans and to identify potential growth areas and their associated road and rail corridors

implement improvement programmes in road and rail corridors where necessary

develop monitoring programmes using baseline information.

Plan options

Specific district planning options include:

Location policies - such as recognising the hierarchy of roads within the district, locating new housing in close proximity to public transport (ie, reducing the need to travel by private motor vehicle and the magnitude of noise generated), or specifying suitable setbacks from major arterial roads. Policies can also be developed to address reverse sensitivity (ie, restricting certain land uses near existing or planned road and rail corridors, placing conditions on resource consents).

Control based measures - such as zoning, site layout to reduce the transmission of, or exposure to, noise or performance standards for noise sensitive activities (eg, demonstrating that the recommended internal sound levels outlined in AS/NZS 2107:2000 - Acoustics can be met).

Control based measures can be used in combination to achieve a specific performance standard such as setback provisions which may be increased or decreased depending on the presence or absence of technical methods, such as noise bunds or acoustic insulation.

Urban design - such as mixed used development that aims to reduce private vehicle use or the siting, orientation and design of buildings that reduces noise impacts.

Urban design and building controls can be used to mitigate land transport related noise effects in newly developed areas by restricting vehicle access or influencing building orientation and layout.

Strategic land use planning - such as development of planning approaches that promote land use patterns that reduce dependency on private vehicles.

Although land transport noise is currently not an issue in every district it is important to recognise that it has the potential to be in the future. Plans and policies need to be deliberately developed with this in mind. For example, plans should include measures to manage future transport and land use developments that may impact on sensitive receivers or create reverse sensitivity effects.

Noise management in future growth areas

Given the direct correlation between noise and urban growth, transport noise should be considered when forecasting and planning for future growth and development in a district or region.

Increased noise levels are directly related to ongoing increases in private car ownership and heavy vehicle use. Consequently, new development that increases traffic volumes in an area may also increase the level of noise experienced by those already living in the area, particularly those who live along major roadways. Noise management approaches need to take into account these cumulative effects.

Another means of addressing noise is to consider the wider transport network itself. Sustainable transport planning aims to reduce reliance on private vehicle use and encourage the use of public transport by establishing land use patterns that reduce the dependency to travel long distances. For example, new subdivisions may be required to develop facilities for cyclists, pedestrians and passenger transport. Increased public transport patronage may also help to reduce noise levels.

2) Policies

District plans should describe why noise is an issue and how it will be addressed. Policies should:

encouraging mixed used development in urban areas (to reduce the need to travel).

The development of a clear policy position is also a useful means to ensure that reverse sensitivity issues are appropriately managed to prevent conflicts arising by limiting or prohibiting the establishment of new land uses where the effects from current activities are likely to result in complaints from new neighbours.

3) Regulatory methods/non-regulatory methods (optional)

Methods should describe how noise management policies will be implemented and explain how acceptable noise levels can be met.

Methods might include, amongst others:

rules that set out specific performance standards to mitigate the effect of noise generated along transport corridors on new dwellings. resource consent conditions may be applicable for some developments

Use of a performance based approach involves establishing an acceptable noise level for particular activities or areas. For example, noise levels in bedrooms should be lower than those in outside play areas.

There are advantages and disadvantages associated with this approach. Advantages include simplicity and universal application. Disadvantages often relate to costs and the inability to cater for future noise levels. This reiterates the importance of long term predictions.

As rail noise is generally more tolerable than road noise, performance standards for new rail corridors are often more lenient compared with roads. In many countries, noise limits for railway corridors are around 5dBA higher than those set for roads.

Specific examples of performance based standards used to control the effects of land transport noise, along with their respective pros and cons, are outlined below. Many of these controls can also be used as conditions on designations.

Setbacks and buffer zones

Site layout can be specified for particular zones through setback provisions. Setbacks provide for noise dissipation reducing the effect of noise on receivers. Setback requirements can be applied to transport corridors as well as buildings.

By making long term transport and development projections, planning authorities can plan for growth and related noise by establishing setback provisions or environmental buffer zones along existing transport corridors or land proposed for urban development. Additionally, transport requiring authorities can designate and acquire corridors of sufficient width to mitigate the adverse effects of noise on future growth areas (eg, through bunding and landscape treatment).

An added benefit of setbacks is that they can subsequently be utilised to provide for walking or cycling tracks, or reserves which can add amenity value.

Setbacks can be inefficient in terms of land loss and cost of purchase and may be costly to maintain.

Districts need to identify who is responsible for these costs (ie, landowner, transport authority, local authority).

Existing land use patterns may preclude the practical imposition of setbacks in urban situations.

Zoning

Zoning can be used to restrict noise sensitive activities in a particular zone and to direct less sensitive activities to locations close to corridors.

Defining zones based on the character and function of an area involves applying a specific ambient noise level to a wider zone, based on the character and function of the area. In using this approach local authorities should identify:

types of uses that are appropriate/not appropriate in areas affected by land transport noise

Rezoning may be necessary where noise levels are increasing to an unsustainable level and cannot be controlled through other means. While it provides guidance as to the future use of the area it can take time to implement and may be unpalatable to existing land owners. Noise affecting existing land owners may also need to be addressed through additional technical measures such as acoustic insulation.

Structural restrictions

Structural controls such as building height or orientation can be used to address noise. Alternatively, the resource consent process can be used if issues are complex or it is difficult to define a single standard or measurable solution. These measures are particularly relevant where development occurs near a road that has barriers or bunds. As barriers need to block the 'line of sight ' to be effective a barrier next to a multi storey building will provide little benefit to residents on upper levels.

4) Environmental results expected (optional)

One of the environmental results expected with the management of noise in plans should be the protection of people and communities from the impacts of land transport noise exposure. Reliance on established acceptable noise levels may help establish whether environmental results expected are being achieved.

5) Monitoring

Territorial authorities need to undertake noise measurement for monitoring purposes, particularly in urban areas. Territorial authorities should state what monitoring will be undertaken and this should form part of a dedicated monitoring programme. Equally, noise provisions included in plans need to be appropriately enforced to ensure their ongoing effectiveness.

noise levels should be assessed at the outset of policy development to provide baseline information to help determine future policy improvements and to establish priorities for ongoing monitoring

the number and type of people affected should be established

territorial authorities should commit to regular reviews of monitoring programmes.

6) Noise mapping

Developing noise maps can be one of the most effective means of monitoring land transport noise and deciding on management strategies.

Noise mapping is a systematic process to 'map' noise in a given area. Noise maps provide a visual interpretation of the location and number of people affected by noise in an area. They are produced for different purposes (eg, the identification of areas where a specific limit value is exceeded), and range from basic contour maps to more sophisticated approaches that incorporate datasets on population density, building fabrication and the location of artificial structures such as noise barriers.

The key steps in the noise mapping process are:

collecting, preparing, storing and querying raw data

computing noise levels using computer models

cumulating noise levels (when there are different sources)

determining noise contours

determining noise effects

presenting the impacts of noise.

Existing noise mapping in New Zealand is currently limited to noise contour mapping around ports and airports but can be extended to include other sensitive environments. Contour maps are less effective at assessing any changes that might affect the noise contours. GIS based mapping that is regularly verified and updated is far more useful.

Some good practice tips for noise mapping include:

Accurate data on noise exposure provides valuable information for impact assessments and for formulating and reviewing noise strategies in district plans.

Noise mapping provides a useful mechanism for measuring and monitoring noise levels. It can also be used to monitor the effectiveness of noise abatement technology. The results can then be compared with predictions made during the noise abatement design stage, or to test predictions made in environmental impact assessments for projects. This is useful for future reference and allows any necessary improvements to be made to abate noise.

Noise mapping can be linked to air quality data mapping

Noise calculations should be backed up by actual measurements when they are taken

Where maps are used to develop a noise mapping strategy, regular updates of the noise maps and comparison between different moments in time are necessary.

Sophisticated noise maps can assist transport and land-use planning by identifying areas exceeding or reaching maximum acceptable noise levels. They can also identify the effect of different types of building layouts on noise dispersal and any quiet zones that need to be preserved, further assisting planning and design.